KR100385922B1 - Method for controlling a call admission by using transmission/reception electric power of base station in code division multiple access system - Google Patents

Abstract

The present invention provides a cell load while guaranteeing call quality in a situation in which various types of services such as voice and data traffic exist in a direct spread-code division multiple access (DS-CDMA) system. To a call admission control method that dynamically adapts to Conventionally, call admission control or channel allocation method based on interference amount has been considered. Most of them have a problem that only voice traffic is considered and the amount of interference from neighboring cells is not considered. In the present invention, the capacity of the code division multiplexing system is determined by the amount of interference and the amount of interference is determined by the load of the current cell. Therefore, call admission control should be a method adapted to the load of the cell. The call admission control method based on the received power at the base station can satisfy this, and the total received power reflects the signal-to-noise ratio, which has the effect of two or two sets. In addition, by assigning different thresholds for each type of traffic, call requests can be controlled by giving priority to desired traffic.

Description

Call Admission Control Method using Transceiver Power of Base Station in Code Division Multiplexing System

The present invention relates to a method for controlling call admission using transmission and reception power of a base station (BS) in a code division multiple access (CDMA) system, and in particular, direct spread-code division multiplexing (Direct). In the Spread-Code Division Multiple Access (DS-CDMA) system, a call admission control method that dynamically adapts to the load of a cell while guaranteeing call quality in the presence of various kinds of services such as voice and data traffic will be.

In conventional direct spread-code division multiplexing systems, capacity is determined by interference from users in a call at the same time. Therefore, to guarantee call quality, interference should be limited to a certain level or less. In this case, the number of users who can simultaneously call is not constant, but the power strengths of the users who are in the call and the neighboring cells in the target cell to which the call belongs acts as an interference, so that each user is the corresponding base station. Even though complete power control is achieved, the number of users who can talk simultaneously becomes flexible. Therefore, there is a need for a call control method that flexibly adapts to the load of the cell. This problem is particularly important in situations where various kinds of traffic exist, because different types of traffic require different call quality and transmission rates.

There are two factors that determine call quality: call blocking rate and call cutting rate. There is a trade-off relationship between these two factors. That is, as more calls are accepted, the call blocking rate decreases and the call cutting rate increases. In particular, call cutting rate is an important factor in determining call quality. The call admission control method should be designed to accommodate as many users as possible while keeping the call cutting rate below a certain level. It also needs to be taken into account because different types of traffic require different call qualities.

In order to solve this problem, call admission control or channel allocation method based on interference amount has been considered. Most of them have a problem that only voice traffic is considered and interference from neighbor cells is not considered.

Accordingly, the present invention has been made to solve the drawbacks of the prior art, and adaptively copes with the load of the cell in an environment where traffic such as voice and data traffic exists in a code division multiplexed mobile communication system to accept a call. And a call admission control method using transmit / receive power of a base station in a code division multiplexing system that rejects (dismisses) to guarantee call quality.

In order to achieve the above object, the present invention provides a code division multiplexing system in which each base station controls a plurality of mobile stations. Selecting a base station of the first step; Requesting to accept the call from the selected base station; A third step of the selected base station determining a required received power corresponding to the requested call; A fourth step of the selected base station comparing the sum of the total received power and the required received power with a predetermined threshold value; A fifth step of accepting the requested call if the sum of the total received power and the required received power is less than a threshold set for the corresponding traffic when a call request is made as a result of the comparison of the fourth step; And a sixth step of rejecting the requested call if the sum of the total received power and the required received power is greater than or equal to a threshold set for the corresponding traffic when a call request is made as a result of the comparison of the fourth step.

1 is a diagram illustrating throughput performance when the threshold values of voice and data are the same.

2 is a hardware configuration diagram for implementing a call admission control method using transmission and reception power of a base station in a code division multiplexing system according to the present invention;

3 is a flowchart illustrating a step-by-step embodiment of a call admission control method using transmit / receive power of a base station in a code division multiplexing system according to the present invention.

<Description of the symbols for the main parts of the drawings>

100: base station 110, 120: first and second mobile stations

Hereinafter, the embodiment of the present invention will be described in detail with reference to the following drawings.

Figure 2 is a hardware configuration for implementing a call admission control method using the transmission and reception power of the base station in the code division multiplexing system according to the present invention, comprising a base station 100 and the first and second mobile stations (110, 120) do.

In the same figure, the base station 100 controls the transmission power of the first and second mobile stations 110 and 120, for example, by a plurality of mobile stations, so that the first and second mobile stations 110 and 120 can provide a constant transmission power. To transmit to the base station 100. When the traffic of the first and second mobile stations 110 and 120 is different, the transmit powers P ₁ and P ₂ of the first and second mobile stations 110 and 120 received by the base station 100 satisfy Equation 3. To maximize system capacity. In addition, since the cell load and the signal-to-noise ratio of each mobile station can be expressed by the total received power at the base station, a call admission control method is proposed based on the total received power at the base station. In addition, we propose a scheme to apply multiple thresholds and a method using queues for data calls that are not sensitive to delay. Using multiple thresholds is a method for accepting more calls by allocating a higher threshold for call admission control for calls requiring priority. Using a queue for a call allowed by the delay improves the overall throughput of the system by storing the rejected call in the queue and serving it at a serviceable point in time.

The code division multiplexing system uses a power control technique to maintain a constant power reaching the base station from the mobile station in order to reduce the amount of interference between each user and the use of batteries. In this situation, under various power control, different bit error rates are required for each traffic and different signal-to-noise ratios are required for each traffic. First, considering the two types of traffic, voice and data, the power strength and signal-to-noise ratio required for voice traffic The power strength and signal-to-noise ratio required by the data traffic The activity factor of each traffic In this case, the signal-to-noise ratio for each traffic is as follows.

here, Indicates the number of voice and data subscribers on the phone, respectively Represent the amount of external interference from the outer cell and the background noise of the receiver, respectively. In the above equation, the molecular term refers to the power that the mobile station's transmit power is received by the base station under power control, and the denominator term refers to the signal and background noise of other users except for its own signal acting as an interference. From Equation 1, the ratio of the required reception power of the base station according to the traffic type can be obtained as Equation 2.

That is, different signal-to-noise ratios for each type of traffic In this case, the power ratio at which the transmit power of each mobile station should be received by the base station must satisfy Equation 2, and if it is satisfied, the number of users that can be used simultaneously in the system is required. Is the maximum. Equation 2 normalizes the required power of one traffic to "1" so that the power of another traffic is constant ( Can be expressed as). This power ratio can be obtained even when there are two or more types of traffic. In other words, Kind of traffic In order to maximize the system capacity of the type of traffic, the required reception power ratio of the base station for each traffic must satisfy the following power ratio.

here, Signal to noise ratio in traffic, Signal to noise ratio in traffic, The silence factor in the traffic, The silence factor in traffic.

In the code division multiplexing system, the call admission control scheme should be made considering the load of the cell. The total received power of the base station may be used as a parameter for measuring the load of the cell. The reason is explained by the following derivation process. In the code division multiplexing system, the amount of interference is determined by the number of concurrent users. That is, the more users, the more power received by the base station by each user, the greater the interference accordingly. Quantitatively, the strength of the received power versus the number of users indicates that the number of voice service users The effective number of users of the data service is The number of effective users of external interference " The maximum capacity of each cell is the amount of interference in the outer cell and the noise of the receiver, and considering the silence coefficient, the maximum capacity of the cell is expressed as follows.

Cell load at cell k Can be expressed as the ratio of the current effective users of the cell to the maximum capacity of the cell, including the amount of external interference, and the total received power at the base station as follows: It is expressed as That is, the total received power at the base station may be used as a parameter representing the cell load.

It can be seen from Equation 5 that the cell load can be expressed as the total received power at the base station. If the total received power at the base station is parameterized in the call admission control, it can be regarded as a cell load-based scheme. The call admission control method based on the total received power can be considered to consider the signal-to-noise ratio in addition to these advantages. That is, generally, the type of traffic at the base station of cell k Since the amount of interference for the traffic of is subtracted its own signal from the total received power, the signal-to-noise ratio Total received power as follows And received power received by the subscriber at the base station to which the subscriber in the call belongs. It can be expressed as

That is, the total received power from equations (5) and (6) Silver cell load And signal-to-noise ratio Reflect at the same time. Therefore, the call admission control method using the total received power as a parameter has the advantage that it is possible to directly control two factors necessary when determining the accept / rejection of the call at the same time.

3 is a flowchart illustrating a step-by-step embodiment of a call admission control method using transmit / receive power of a base station in a code division multiplexing system according to the present invention.

First, when a call is generated, each mobile station involved in the call generation selects a base station whose propagation attenuation is minimum as its base station and requests the base station to accept the call (step 10).

The selected base station then selects the appropriate required received power that satisfies Equation 1 for the requested call. (Step 20).

The selected base station is the total received power And the required receive power Plus the set threshold (Step 30). In this case, the threshold should be set below the value required by the system and the maximum value of this threshold. Can be obtained as

First, the required reception power of the reference traffic is normalized to '1'. For other traffic, the value in Equation 3 becomes the required receive power, and the signal-to-noise ratio required for each traffic type is calculated. The system must:

Therefore, the minimum value of the signal-to-noise ratio to satisfy the call quality is when the equation is established in Equation 7, and the total received power value is the maximum value of the threshold. Becomes If the required received power of the reference traffic is not "1" If the maximum value of the threshold is Becomes

On the other hand, in the present invention, the threshold value different for each traffic type Call admission control by assigning priority to the desired traffic. In other words, for traffic that gives priority, By setting it closer to the value, you accept more calls than other traffic.

If the sum of the total received power measured at the call request and the calculated required received power is less than the threshold set for the corresponding traffic, the requested call is accepted (step 40).

On the other hand, if it is above the set threshold, the requested call is rejected (rejected) (step 50).

It is determined whether the rejected call is a data call allowed for delay (step 60).

As a result of the determination of step 60, if the rejected call is a data call allowing delay, the call is stored in a queue and serviced at the serviceable time (step 70).

As described above, in the present invention, the capacity of the code division multiplexing system is determined by the amount of interference, and the amount of interference is determined by the load of the current cell. Therefore, call admission control should be a method adapted to the load of the cell. The call admission control method based on the received power at the base station can satisfy this, and the total received power reflects the signal-to-noise ratio, which has the effect of two or two sets. In addition, by assigning different thresholds for each type of traffic, call requests can be controlled by giving priority to desired traffic. In addition, in the case of a call allowing a delay, an increase in throughput may be obtained as shown in FIG. 1 by storing in a queue.

Claims (5)

delete A code division multiplexing system in which each of a plurality of base stations controls a plurality of mobile stations, A first step in which, when a call is generated, each mobile station involved in the call generation selects a base station whose propagation attenuation is minimized as its base station; Requesting to accept the call from the selected base station; A third step of the selected base station determining a required received power corresponding to the requested call; A fourth step of the selected base station comparing the sum of the total received power and the required received power with a predetermined threshold value; A fifth step of accepting the requested call if the sum of the total received power and the required received power is less than a threshold set for the corresponding traffic when a call request is made as a result of the comparison of the fourth step; And And a sixth step of rejecting the requested call if the sum of the total received power and the required received power is greater than or equal to a threshold set for the corresponding traffic when a call request is made. The third step is to determine the required received power ratio " Call admission control method using the transmission and reception power of the base station in the code division multiplexing system to determine. The method of claim 2, And the threshold is set below a value required by the system. The method of claim 2, The maximum value of the threshold is " "A call admission control method using transmit / receive power of a base station in an encoding division multiplexing system. The method of claim 2, A thirty-first step of determining whether the rejected call is a data call allowed for delay; And As a result of the determination of the thirty-first step, if the rejected call is a data call allowing a delay, the call is stored in a queue and is serviced at a serviceable time point. Call admission control method.